Modes and Environment Variables
Modes
Mode is an important concept in Vue CLI projects. By default, there are three modes:
development
is used byvue-cli-service serve
test
is used byvue-cli-service test:unit
production
is used byvue-cli-service build
andvue-cli-service test:e2e
You can overwrite the default mode used for a command by passing the --mode
option flag. For example, if you want to use development variables in the build command:
vue-cli-service build --mode development
When running vue-cli-service
, environment variables are loaded from all corresponding files. If they don't contain a NODE_ENV
variable, it will be set accordingly. For example, NODE_ENV
will be set to "production"
in production mode, "test"
in test mode, and defaults to "development"
otherwise.
Then NODE_ENV
will determine the primary mode your app is running in - development, production or test - and consequently, what kind of webpack config will be created.
With NODE_ENV
set to "test" for example, Vue CLI creates a webpack config that is intended to be used and optimized for unit tests. It doesn't process images and other assets that are unnecessary for unit tests.
Similarly, NODE_ENV=development
creates a webpack configuration which enables HMR, doesn't hash assets or create vendor bundles in order to allow for fast re-builds when running a dev server.
When you are running vue-cli-service build
, your NODE_ENV
should always be set to "production" to obtain an app ready for deployment, regardless of the environment you're deploying to.
NODE_ENV
If you have a default NODE_ENV
in your environment, you should either remove it or explicitly set NODE_ENV
when running vue-cli-service
commands.
Environment Variables
You can specify env variables by placing the following files in your project root:
.env # loaded in all cases
.env.local # loaded in all cases, ignored by git
.env.[mode] # only loaded in specified mode
.env.[mode].local # only loaded in specified mode, ignored by git
An env file simply contains key=value pairs of environment variables:
FOO=bar
VUE_APP_SECRET=secret
Note that only variables that start with VUE_APP_
will be statically embedded into the client bundle with webpack.DefinePlugin
.
For more detailed env parsing rules, please refer to the documentation of dotenv
. We also use dotenv-expand for variable expansion (available in Vue CLI 3.5+).
Loaded variables will become available to all vue-cli-service
commands, plugins and dependencies.
Env Loading Priorities
An env file for a specific mode (e.g. .env.production
) will take higher priority than a generic one (e.g. .env
).
In addition, environment variables that already exist when Vue CLI is executed have the highest priority and will not be overwritten by .env
files.
.env
files are loaded at the start of vue-cli-service
. Restart the service after making changes.
Example: Staging Mode
Assuming we have an app with the following .env
file:
VUE_APP_TITLE=My App
And the following .env.staging
file:
NODE_ENV=production
VUE_APP_TITLE=My App (staging)
vue-cli-service build
builds a production app, loading.env
,.env.production
and.env.production.local
if they are present;vue-cli-service build --mode staging
builds a production app in staging mode, using.env
,.env.staging
and.env.staging.local
if they are present.
In both cases, the app is built as a production app because of the NODE_ENV
, but in the staging version, process.env.VUE_APP_TITLE
is overwritten with a different value.
Using Env Variables in Client-side Code
You can access env variables in your application code:
console.log(process.env.VUE_APP_SECRET)
During build, process.env.VUE_APP_SECRET
will be replaced by the corresponding value. In the case of VUE_APP_SECRET=secret
, it will be replaced by "secret"
.
In addition to VUE_APP_*
variables, there are also two special variables that will always be available in your app code:
NODE_ENV
- this will be one of"development"
,"production"
or"test"
depending on the mode the app is running in.BASE_URL
- this corresponds to thepublicPath
option invue.config.js
and is the base path your app is deployed at.
All resolved env variables will be available inside public/index.html
as discussed in HTML - Interpolation.
You can have computed env vars in your vue.config.js
file. They still need to be prefixed with VUE_APP_
. This is useful for version info
process.env.VUE_APP_VERSION = require('./package.json').version
module.exports = {
// config
}
Local Only Variables
Sometimes you might have env variables that should not be committed into the codebase, especially if your project is hosted in a public repository. In that case you should use an .env.local
file instead. Local env files are ignored in .gitignore
by default.
.local
can also be appended to mode-specific env files, for example .env.development.local
will be loaded during development, and is ignored by git.